On Tue, Aug 28, 2018 at 03:39:01PM -0700, Randy Dunlap wrote: > Just a question, please... > > On 08/28/2018 03:27 PM, Matthew Wilcox wrote: > > > > diff --git a/include/linux/xarray.h b/include/linux/xarray.h > > index c74556ea4258..d1b383f3063f 100644 > > --- a/include/linux/xarray.h > > +++ b/include/linux/xarray.h > > @@ -150,6 +150,54 @@ static inline int xa_err(void *entry) > > return 0; > > } > > > > +/** > > + * xa_tag_pointer() - Create an XArray entry for a tagged pointer. > > + * @p: Plain pointer. > > + * @tag: Tag value (0, 1 or 3). > > + * > > What's wrong with a tag value of 2? That conflicts with the XArray's internal entries and you get a WARN_ON when you try to store it in the array. > and what happens when one is used? [I don't see anything preventing that.] Right, there's nothing preventing you from using the value 5 or 19 or 16777216 either ... I did put in a WARN_ON_ONCE to begin with, but decided that was unnecessary. Right now our only user uses 0 and 1, so even documenting 3 as a possibility isn't _necessary_, but some day somebody is going to want to add FILE_NOT_FOUND https://thedailywtf.com/articles/What_Is_Truth_0x3f_
